Exam 222222

Question 1

What are genes made out of?

Answer 1

DNA

Question 2

Where are genes found?

Answer 2

On the chromosome

Question 3

What is the basic structure of DNA made out of?

Answer 3

Sugar connected to a phosphate molecule and a second molecule known as a base.

Question 4

What are bases called?

Answer 4

Nucleotides

Question 5

How many different “flavors” of nucleotides are there?

Answer 5

A, T, C, G

Question 6

What does DNA look like?

Answer 6

A double helix of two ling chain of nucleotides, weak bonds between adjacent bases called hydrogen bonds how the two chains together.

Question 7

How does a mutation in a gene happen?

Answer 7

During replication, if a base is incorrectly placed or a new base is added or a base is deleted

Question 8

Why do some mutations show in the phenotype and others dont?

Answer 8

The genetic code is redundant

Question 9

Are mutations always bad?

Answer 9

Many mutations are detrimental, but some are beneficial and so are favored by natural selection. Indeed, mutation is the basic source of the genetic variation upon which selection acts.

Question 10

In what kinds of cells must DNA mutations occur if they are to be inherited by a child from one of her parents?

Answer 10

Parents egg or sperm cells

Question 11

Would evolutionary change be more likely/faster if the rate of mutation was to increase? Explain your answer.

Answer 11

Yes.

Question 12

What is the basic chemistry of life?

Answer 12

nucleic acids (DNA and RNA), carbohydrates, lipids and proteins.

Question 13

What are proteins made out of?

Answer 13

• Proteins are made up of units called amino acids. Each amino acid (there are 20 in nature) has a unique side group. Amino acids combine with one another via a dehydration reaction to form a polypeptide chain. The 3-D conformation of the chain represents a functional protein, truly one of the basic building blocks of a phenotype.

Question 14

What is the process of transcription?

Answer 14

Triplets of bases (groups of three, such as ACC or TAG) code for (or correspond to) particular amino acids. Remember, there are 20 of the latter in nature.

In the process of transcription, the DNA message in triplets of bases is converted into a codon message in mRNA (or messenger RNA). mRNA is a single strand of nucleotides, in which the sugar ribose replaces deoxyribose and the base U replaces the base T.

Question 15

What is the process of translation?

Answer 15

In the process of translation (which occurs on cytoplasmic structures called ribosomes), mRNA combines with tRNA (or transfer RNA), the latter carrying specific amino acids

Where mRNA codons and tRNA amino acids match, adjacent amino acids connect to one another via dehydration reactions to form a protein (or, more correctly, a polypeptide chain which will later fold to form a protein).

Question 16

Why is the genetic code redundant?

Answer 16

The genetic code is said to be redundant, meaning that more than one codon is associated with each of the 20 amino acids. And that means that a mutation in DNA (let’s say an A base replacing a C base) doesn’t necessarily change the protein for which a gene codes. This redundancy is why mutations don’t always alter phenotypes.

Question 17

What is the central dogma for molecular biology?

Answer 17

The central dogma of molecular biology states that the information needed to create a phenotype flows from DNA to RNA to protein. Information cannot flow in the reverse direction (and so, contrary to Lamarck’s idea, acquired changes to the physical phenotype through use/disuse cannot be inherited via changes in DNA bases).

Question 18

What are retroviruses and how do they differ from regular viruses?

Answer 18

Retroviruses are different: information flows from RNA to DNA, e.g., in HIV, the virus that causes AIDS.

Question 19

What is one way to treat AIDS?

Answer 19

Blocking such “reverse transcription” is one treatment for AIDS, e.g., AZT therapy. However, mutations in the RNA of HIV can result in resistance to drug therapies

Question 20

What is epigenetics?

Answer 20

Remember Lamarck? “Acquired characters cannot be inherited.” It is true that, say, genetic changes that occur in a skin tumor can’t be inherited. But, changes to proteins on chromosomes – not the DNA bases themselves – that alter gene activity may be passed to offspring if those changes are present in sex cells.

For example, chemicals pollutants given to a pregnant female mouse may lead to changes in these proteins in the cells of her fetus. After birth, her offspring may pass these altered proteins on to their own young. This exciting branch of biology is called “epigenetics.”

Remember, we’re not talking about mutational changes to DNA bases, e.g., replacing an A with a C.

Question 21

What is cell theory?

Answer 21

all living things are made of one or more cells. Thus, many biologists do not consider viruses to be living things – viruses aren’t cells.

Question 22

what is a cell?

Answer 22

Cells are “bags of life” separated from the outside world. An outer membrane (made of fats and proteins) acts as a barrier with “gates.” Not all materials can enter or leave through the gates in the membrane – in other words, these gates can be selective.

Question 23

What are organelles?

Answer 23

Within cells, different structures, called organelles (“little organs”), perform different tasks.

Question 24

What are ribosomes?

Answer 24

Ribosomes are the sites of protein synthesis (where mRNA codons and tRNA carrying amino acids come together in the process of translation).

Question 25

What are mitochondria?

Answer 25

Mitochondria produce energy by respiration: glucose + oxygen -> carbon dioxide + ATP. We can think of ATP as energy in storage (a bit like a battery). Useable energy is released when ATP -> ADP (i.e., when ATP loses one of its phosphate groups – triphosphate becomes diphosphate)

Question 26

What is chloroplast?

Answer 26

Chloroplasts (in plants only) produce sugars by photosynthesis: carbon dioxide + water + sunlight -> sugars + oxygen.

Question 27

What is the difference between eukaryotic cells and prokaryotic cells?

Answer 27

Cells with a distinct nucleus and organelles surrounded by membranes are called eukaryotes. Cells without, such as bacteria, are called prokaryotes.

Eukaryotes and prokaryotes differ in many aspects of how they “earn a living.” Eukaryotes are like slow, fancy cadillacs whereas prokaryotes are more like speedy, stripped-down race cars.

Question 28

All cells divide by the process of…

Answer 28

Mitosis

Question 29

All cells divide by the process of Mitosis except..

Answer 29

With the exception of cells that produce sperm and eggs (sex cells, or gametes), all cells divide by mitosis.

Question 30

What is the process of Mitosis?

Answer 30

Mitosis is part of the cell cycle, the stages of which are labeled as G1, S, G2 and mitosis. A cell grows and does its jobs (G1), copies its DNA (S) and then gets ready to divide (G2)

Question 31

What is the cell cycle controlled by?

Answer 31

The cell cycle is controlled by genes – lots of genes. Two kinds of genes are particularly important (but I stress they aren’t the only genes involved). Genes called oncogenes promote mitosis, whereas tumor-suppressor genes inhibit mitosis.

Question 32

What is the relationship between cancer and cell division?

Answer 32

Cancer arises when regulation of the cell cycle fails and mitosis becomes uncontrolled. For example, genes that either promote or inhibit mitosis may suffer mutations and so not function properly. In an imperfect analogy to traffic signals, it is as if the green light is always on and/or the red light is always off.

Cancer is a variable disease with variable causes, including exposure to environmental carcinogens such as tobacco smoke and the rays coming from tanning beds. Not too many cancers are caused by genetic changes that can be inherited, but more may be caused by infectious agents (such as viruses) than we once thought.

Question 33

What kind of treatments are available for cancer patients?

Answer 33

Cancer is harder to treat when secondary tumors have arisen through metastasis, but new treatments for cancer at all stages are under constant development. Standard therapies involve surgery and/or the use of radiation and/or drugs (chemotherapies) to slow or halt cell division. For example, the drug Taxol disrupts the little spindles that move chromosomes during mitosis.

Newer therapies are more targeted. For example, the drug Avastin blocks angiogenesis, starving tumor cells and making metastasis less likely. Another approach is to block the responses of cancer cells to molecules that occur naturally in the body and which stimulate cell division.

And a lot of research is being devoted to ways in which the body’s own defense cells can be stimulated to attack cancer cells.

Perhaps most exciting are developments in which the mutations in an individual’s tumor are identified and then a mutation-specific therapy is given – we might call this individualized therapy.

Question 34

How many Americans will have cancer in their lifetime?

Answer 34

Despite progress with particular kinds of cancer, the disease overall remains the second leading cause of death in the U.S. (heart disease is number one, but not by much of a lead), and the most common kind of cancer is that of the skin followed by the lung. About one out of every three Americans will develop cancer if they live long enough. Of course, developing cancer isn’t the same as dying from cancer.

Question 35

What is ISICU?

Answer 35

The basic strategy underlying applied genetics is what we’ll call ISICU – Identify, Sequence, Isolate, Copy, Use.

Identify and sequence the bases in genes of interest.

Isolate the gene of interest – restriction enzymes (think of them as “DNA scissors”) recognize particular sequences of bases (A, C, T and G) and cut the DNA where those sequences occur. Thus, a gene can be removed from its chromosome.

With a gene isolated from its chromosome by cutting it free with restriction enzymes, we can use the polymerase chain reaction (or PCR) to produce millions of copies accurately, quickly and cheaply. PCR basically mimics in a machine the natural process by which DNA is replicated in cells. Now we are ready to use that gene.

Question 36

What does it mean to have DNA that is recombinant?

Answer 36

DNA that carries a gene from a different species is said to be recombinant.

Question 37

What does it mean to be transgenic?

Answer 37

An individual carrying a gene from a different species is said to be transgenic

Question 38

How does gene transferring work?

Answer 38

With a gene isolated, we can use PCR to produce millions of copies accurately, quickly and cheaply.

Heres an example: Using restriction enzymes, a copy of a gene of interest is spliced into a plasmid, which is a bacterial mini-chromosome. The plasmid is then put into a bacterial cell. That recipient cell, and all of its descendants (produced by mitosis), will copy the foreign gene and then can be made to manufacture the protein for which it codes. In this way, we can generate transgenic bacteria with recombinant DNA that produce, say, human insulin, which can be used to treat Type I diabetes (also called juvenile or early-onset diabetes). This process is the core of our current biotech industry.

Question 39

What is gene editing?

Answer 39

It relies on a mechanism evolved by bacteria to help them fend of attacks by viruses (a mechanism that is different from the one that involves restriction enzymes and that we discussed earlier).

This mechanism, called CRISPR-Cas9, is already being used in research, but what about the possibility of using it to, say, fix malfunctioning genes in humans?

There’s a lot of excitement about using CRISPR-Cas9 to fix wonky genes in human eggs, although pretty much all scientists agree that it is far too early to do this clinically. But research is being conducted.

Question 40

How is DNA helping to catch criminals?

Answer 40

Repetitive sequences of bases that don’t code for proteins (called tandem repeat units) can be cut out of their chromosomes, separated and stained to make them visible. They can then be used as DNA fingerprints because they are so incredibly variable among individuals in how many repeating units they possess. I stress that only stretches of DNA that do not code for proteins can be used in this way.

By comparing DNA fingerprints among defendants in a criminal case, we can exclude those for whom we obtain no genetic match. Wrongly imprisoned people have been released from jail thanks to such exclusion.

When we find a match, statistical methods can be used to estimate how likely that match may be due to chance. The smaller that estimate, the more certain we can be that the match is real.

Question 41

Is taking samples from those who are arrested (without being found guilty) legal?

Answer 41

The Supreme Court ruled recently that taking such samples is consistent with the U.S. Constitution and the Bill of Rights.